Answered by Shaykh Faraz Rabbani
If we miss one fast in Ramadan for some reason then how many do we have to keep in a non-Ramadan month to make up for it?
It is obligatory to make up the missed fast, one for one.
It may be that one has to fast 60 consecutive days as expiation (kaffara), if one deliberately ate, drank or had sexual intercourse while fasting in Ramadan, as outlined in the recent post ‘The Fiqh of Fasting.’
And Allah alone gives success.